1. Field of the Invention
This invention relates generally to pulse combustion apparatus (for example with heaters of the pulse combustion type) and is more particularly concerned with improvements in and relating to exhaust systems for pulse combustion apparatus.
2. Description of Prior Art
United States patent literature contains numerous examples of prior art pulse combustion apparatus. Typically, such an apparatus includes a combustion chamber and an exhaust pipe which which forms a resonant system with the combustion chamber. the apparatus operates on a cycle in which a fuel charge is admitted to the combustion chamber and ignited. The charge then expands into the exhaust pipe causing a partial vaccum transient in the combustion chamber, which both assists in drawing in a fresh fuel charge and causes high temperature gas to be drawn back into the combustion chamber from the exhaust pipe. The fresh fuel charge is ignited spontaneously from flame fronts in the returning high temperature gas, thereby establishing the next cycle. Accordingly, the apparatus is self-sustaining after initial ignition. In a pulse combustion heater, a fluid to be heated is brought into heat exchange relationship with the exhaust pipe; usually, a heat exchanger is provided downstream of the exhaust pipe to improve the efficiency of heat transfer from the combustion gases to the fluid.
By way of example, pulse combustion heaters are disclosed in my U.S. Pats. Nos. 3,267,985, 4,241,720 and 4,241,723. The various forms of apparatus disclosed are intended primarily (but not exclusively) for use as boilers, i.e. for heating water. However, it has been proposed to use this type of apparatus specifically for heating air. Examples of this type of apparatus are shown in my U.S. Pats. Nos. 2,916,032, 4,309,977 and 4,336,791.
An object of the present invention is to provide improvements in and relating to exhaust systems for pulse combustion apparatus.